The present invention pertains primarily to integral skin foams, and more particularly to color or light stable integral skin polyurethane foams.
The following cited references are believed to be representative of the state of the art:
______________________________________ U.S. Pat. No. Inventor(s) Issued ______________________________________ 3,182,104 Civik May 4, 1965 3,422,036 Ellegast et al January 14, 1969 3,473,951 De Rossi et al October 21, 1969 3,476,933 Mendelsohn November 4, 1969 3,645,924 Fogiel February 29, 1972 3,655,597 Strassel April 11, 1972 3,769,244 Hashimoto October 30, 1973 3,775,350 Juhas November 27, 1973 3,814,707 Moller June 4, 1974 3,925,526 Haas December 9, 1975 3,993,608 Wells November 23, 1976 4,006,124 Welte et al February 1, 1977 4,025,466 Jourquin et al May 24, 1977 4,150,206 Jourquin et al April 17, 1979 ______________________________________ Canadian Patent No. 580,788 to Parker et al, issued August 4, 1959. United Kingdom Patent No. Inventor(s) Issued ______________________________________ 891,007 Lowe et al March 7, 1962 900,392 Cowdrey et al July 4, 1962 1,009,965 -- November 17, 1965 ______________________________________
Generally, integral skin polyurethane foam is used on articles which must be elastic, flexible, relatively impermeable, have good resistance to tear and plastic deformation, a compact surface or skin, and a cellular internal structure. Typical of such articles are many of the parts used in automobiles such as arm rests, crash pad covers, and steering wheels. The one step molding operation for integral skin polyurethane foam replaced to some extent the two step process in which a separate skin was first molded, and then a non-skinning urethane foam was molded inside the skin to form the finished product.
The surface or skin of an integral skin foam article comprises a substantially nonexpanded elastomer layer which is both compact and impervious, while internally, the article comprises a flexible and elastic cellular mass forming a protective padding which provides insulation against shocks and vibrations. For example, a steering wheel comprising integral skin urethane foam would have a skin that may have the appearance of leather, have a pleasant feel, be relatively resilient when handled, provide vibration absorption and thermal isolation, and also be somewhat flexible in the event of an accident.
Originally, most integral skin polyurethane foam parts were produced in just a few colors, namely black, brown, or gray; and then if some other surface color was desired, the part would be painted. However, painted wheels are considerably more expensive to produce than unpainted wheels for reasons that should be readily apparent. Further, there is very often some problem with paint adhesion and paint wear in actual use due to abrasion and other effects of repeated handling. As a result of these problems, efforts have been directed at producing integrally colored integral skin foam parts, that is, parts in which the color is molded right into the part so that the entire part bears the same color inside and out.
Normal integral skin polyurethane foams, because of the presence of aromatic diisocyanates in the reacting mixture, have poor color stability and usually will yellow severely when exposed to ultraviolet light or other visible radiation. Efforts at preparing such foams using aliphatic diisocyanates have met with rather limited success since although the foams produced are relatively color stable, they are slow reacting and thus are difficult to incorporate into commercial manufacturing processes and also are economically unattractive or prohibitive.
It is a principal object of the present invention therefore to provide a color stable integral skin polyurethane foam.
Another object of the present invention is to provide a color stable integral skin foam formulation which uses aliphatic diisocyanates and which reacts at a reasonable rate.
It is thus a further object of the present invention to provide a foam which because of its reasonable reaction rate is economically attractive to produce. Other objects, features and advantages of the present invention will become apparent from the subsequent description and examples, and the appended claims.